Effect Of Perinereis Aibuhitensis On The Degradation Of Three Kinds Of Pahs In Suaeda Heteroptera And Oil-degradation Bacteria Models

In recent years, a large number of persistent organic pollutants have discharged into the ocean through domestic sewage, industrial wastewater, and maritime transport leak. These pollutants have caused the degradation of coastal wetland, and further affected human beings’ health through food chain.In this study, we chosen Perinereis aibuhitensis, Suaeda heteroptera and oil-degradation bacteria as experimental subjects and established three different combined bioremediation models. The depredating rate of phenanthrene as well as bacteria number in sediment among different bioremediation models were examined using wetland microcosm method, and the bioaccumulation and bioavailability of phenanthrene in P. aibuhitensis with static method were detected, in order to investigate the enhancement of marine polychaetes in phenanthrene degradation. In addition, the removal efficiency of benzo(a)pyrene and 3-methylphenanthrene in nereid-suaeda-bacteriacombined bioremediation mode was examined. The results in this study will provide data support for combined bioremediation in PAHs contaminated intertidal area.The main results of this research are shown as follows:1. The bioaccumulation of phenanthrene in P. aibuhitensis increased significantly with the concentration of phenanthrene. The maximum content of phenanthrene in P. aibuhitensis was 11.1±0.5 mg kg-1. Overall, the content of phenanthrene in P. aibuhitensis increased at the first 9 days, then the content decreased with the time prolonging. At 19 d the content was 2.14±0.2 mg kg-1, having no significant difference compared to control group.It indicated that the metabolic rate of phenanthrene is higher than the enrichment rate in the body of P. aibuhitensis.the bioaccumulation parameters(K1, K2) were 0.0197 and 0.165. Bioconcentration factors(BCF) for phenanthrene in P. aibuhitensis was 0.12.2. The depredating rate of phenanthrene as well as bacteria number in sediment among different bioremediation models were examined using wetland microcosm and chronic toxicity method. The results indicated that the degradation rate of phenanthrene in three bioremediation modes was significantly different, and the degradation rate from highest to lowest was nereid-suaeda- bacteria>suaeda-bacteria>nereid. At 30 d the degradation rate in nereid-suaeda-bacteria and suaeda-bacteria model reached 97.02% and 93.93%, respectively. The average degradation rate in each model was decreased with time prolonging. P. aibuhitensis had significantly enhanced effect on biotic and abiotic factors to remediation of phenanthrene,which reached 14.32% and 20.08%, respectively. At 0-5d the total number of oil-degradation bacteria in nereid-suaeda-bacteria model was much more than that in suaeda-bacteria model, but the bacteria number in these two models fell sharply to the level of control at 20-30 d.3. The removal efficiency of different concentration of benzo(a)pyreneand 3-methylphenanthrenein nereid-suaeda-bacteria combined bioremediation model was examined under laboratory conditions.The results show that with the extension of time, the benzo(a)pyrene concentration and the removal efficiency decreases gradually,.At 5 d, removal efficiency in different concentration of benzene(a)pyrene(70 mg kg-1、140 mg kg-1and 220 mg kg-1) were 65.71%, 78.57% and 73.64% respectively.At 30 d total degradation rate of benzo(a)pyrene in each group were 88.6%, 92.1% and 91.4% respectively. benzo(a) pyrene cannot be degradated in Low concentration group(<140 mg kg-1); benzo(a)pyrene degradation rate is upregulated with the decrease concentration of benzo(a)pyrene in high concentration group(≥140 mg kg-1).the tendency of degradation rate of 3-methylphenanthrene and the concentration of 3-methylphenanthrene were same as that of benzo(a)pyrene.At 5 d, degradation rate in different concentration of 3-methylphenanthrene(1mg kg-1、1.5 mg kg-1and 3.5 mg kg-1) were 30.0%、33.3%and 51.4% respectively. At 30 d total degradation rate in each group were 63.0%、63.3%、77.1% respectively. When-the concentration of 3-methylphenanthrene is lower than 3.5 mg kg-1, the degradation rate of 3-methylphenanthrene increased with the substrate concentration of pollutants.In general, P. aibuhitensis has a strong bioaccumulation ability of phenanthrene, andthe existence of marine polychaetes could improve hydrocarbon degradation ability of bacteria in sediment.The degradation rate of PAHs in combined bioremediation models from highest to lowest was phenanthrene>benzo(a)pyrene>3-methylphenanthrene.